This invention relates to a containing case for a luminous display for use in a motor vehicle instrument panel and particularly to such a case wherein the display brightness may be controlled according to ambient light intensity.
The use of luminous digital displays, in which numbers are formed by the powering of selected fluorescent tubes, light emitting diodes or similar devices, is increasing in many devices which include numerical displays. The use of such displays is beginning to be seen in motor vehicle instrument panels; although the great range of ambient light conditions encountered by a vehicle operator makes it desirable to have some form of brightness control for the display. Ideally, in daylight, such brightness control would be capable of responding to ambient light conditions to smoothly vary the display brightness in accordance therewith.
Thus there is a need, in such devices, for apparatus capable of sensing the ambient light level outside the case in which the lighted display is contained and communicating such light intensity information to an appropriate device in the electrical circuitry which controls the display brightness. Such apparatus must accurately and reliably convey the ambient light intensity information without being substantially affected by the light of the display itself and should ideally be nonelectrical in nature so that all electrical components may be confined to one or more electrical circuit boards within the case. It would also, ideally, be capable of being formed directly in the case itself with a minimum number of added parts to reduce cost. In addition, such apparatus should not unduly complicate the assembly of the device.